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//===--- CFG.cpp - Classes for representing and building CFGs----*- C++ -*-===//
//
// The LLVM Compiler Infrastructure
//
// This file was developed by Ted Kremenek and is distributed under
// the University of Illinois Open Source License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file defines the CFG and CFGBuilder classes for representing and
// building Control-Flow Graphs (CFGs) from ASTs.
//
//===----------------------------------------------------------------------===//
#include "clang/AST/CFG.h"
#include "clang/AST/Expr.h"
#include "clang/AST/StmtVisitor.h"
#include "clang/AST/PrettyPrinter.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/Support/GraphWriter.h"
#include "llvm/Config/config.h"
#include <iostream>
#include <iomanip>
#include <algorithm>
#include <sstream>
using namespace clang;
namespace {
// SaveAndRestore - A utility class that uses RIIA to save and restore
// the value of a variable.
template<typename T>
struct SaveAndRestore {
SaveAndRestore(T& x) : X(x), old_value(x) {}
~SaveAndRestore() { X = old_value; }
T get() { return old_value; }
T& X;
T old_value;
};
/// CFGBuilder - This class is implements CFG construction from an AST.
/// The builder is stateful: an instance of the builder should be used to only
/// construct a single CFG.
///
/// Example usage:
///
/// CFGBuilder builder;
/// CFG* cfg = builder.BuildAST(stmt1);
///
/// CFG construction is done via a recursive walk of an AST.
/// We actually parse the AST in reverse order so that the successor
/// of a basic block is constructed prior to its predecessor. This
/// allows us to nicely capture implicit fall-throughs without extra
/// basic blocks.
///
class CFGBuilder : public StmtVisitor<CFGBuilder,CFGBlock*> {
CFG* cfg;
CFGBlock* Block;
CFGBlock* Succ;
CFGBlock* ContinueTargetBlock;
CFGBlock* BreakTargetBlock;
CFGBlock* SwitchTerminatedBlock;
// LabelMap records the mapping from Label expressions to their blocks.
typedef llvm::DenseMap<LabelStmt*,CFGBlock*> LabelMapTy;
LabelMapTy LabelMap;
// A list of blocks that end with a "goto" that must be backpatched to
// their resolved targets upon completion of CFG construction.
typedef std::vector<CFGBlock*> BackpatchBlocksTy;
BackpatchBlocksTy BackpatchBlocks;
// A list of labels whose address has been taken (for indirect gotos).
typedef llvm::SmallPtrSet<LabelStmt*,5> LabelSetTy;
LabelSetTy AddressTakenLabels;
public:
explicit CFGBuilder() : cfg(NULL), Block(NULL), Succ(NULL),
ContinueTargetBlock(NULL), BreakTargetBlock(NULL),
SwitchTerminatedBlock(NULL) {
// Create an empty CFG.
cfg = new CFG();
}
~CFGBuilder() { delete cfg; }
// buildCFG - Used by external clients to construct the CFG.
CFG* buildCFG(Stmt* Statement);
// Visitors to walk an AST and construct the CFG. Called by
// buildCFG. Do not call directly!
CFGBlock* VisitStmt(Stmt* Statement);
CFGBlock* VisitNullStmt(NullStmt* Statement);
CFGBlock* VisitCompoundStmt(CompoundStmt* C);
CFGBlock* VisitIfStmt(IfStmt* I);
CFGBlock* VisitReturnStmt(ReturnStmt* R);
CFGBlock* VisitLabelStmt(LabelStmt* L);
CFGBlock* VisitGotoStmt(GotoStmt* G);
CFGBlock* VisitForStmt(ForStmt* F);
CFGBlock* VisitWhileStmt(WhileStmt* W);
CFGBlock* VisitDoStmt(DoStmt* D);
CFGBlock* VisitContinueStmt(ContinueStmt* C);
CFGBlock* VisitBreakStmt(BreakStmt* B);
CFGBlock* VisitSwitchStmt(SwitchStmt* S);
CFGBlock* VisitSwitchCase(SwitchCase* S);
CFGBlock* VisitIndirectGotoStmt(IndirectGotoStmt* I);
private:
CFGBlock* createBlock(bool add_successor = true);
CFGBlock* addStmt(Stmt* S);
CFGBlock* WalkAST(Stmt* S, bool AlwaysAddStmt);
CFGBlock* WalkAST_VisitChildren(Stmt* S);
CFGBlock* WalkAST_VisitVarDecl(VarDecl* D);
CFGBlock* WalkAST_VisitStmtExpr(StmtExpr* S);
CFGBlock* WalkAST_VisitCallExpr(CallExpr* C);
void FinishBlock(CFGBlock* B);
};
/// BuildCFG - Constructs a CFG from an AST (a Stmt*). The AST can
/// represent an arbitrary statement. Examples include a single expression
/// or a function body (compound statement). The ownership of the returned
/// CFG is transferred to the caller. If CFG construction fails, this method
/// returns NULL.
CFG* CFGBuilder::buildCFG(Stmt* Statement) {
assert (cfg);
if (!Statement) return NULL;
// Create an empty block that will serve as the exit block for the CFG.
// Since this is the first block added to the CFG, it will be implicitly
// registered as the exit block.
Succ = createBlock();
assert (Succ == &cfg->getExit());
Block = NULL; // the EXIT block is empty. Create all other blocks lazily.
// Visit the statements and create the CFG.
if (CFGBlock* B = Visit(Statement)) {
// Finalize the last constructed block. This usually involves
// reversing the order of the statements in the block.
if (Block) FinishBlock(B);
// Backpatch the gotos whose label -> block mappings we didn't know
// when we encountered them.
for (BackpatchBlocksTy::iterator I = BackpatchBlocks.begin(),
E = BackpatchBlocks.end(); I != E; ++I ) {
CFGBlock* B = *I;
GotoStmt* G = cast<GotoStmt>(B->getTerminator());
LabelMapTy::iterator LI = LabelMap.find(G->getLabel());
// If there is no target for the goto, then we are looking at an
// incomplete AST. Handle this by not registering a successor.
if (LI == LabelMap.end()) continue;
B->addSuccessor(LI->second);
}
// Add successors to the Indirect Goto Dispatch block (if we have one).
if (CFGBlock* B = cfg->getIndirectGotoBlock())
for (LabelSetTy::iterator I = AddressTakenLabels.begin(),
E = AddressTakenLabels.end(); I != E; ++I ) {
// Lookup the target block.
LabelMapTy::iterator LI = LabelMap.find(*I);
// If there is no target block that contains label, then we are looking
// at an incomplete AST. Handle this by not registering a successor.
if (LI == LabelMap.end()) continue;
B->addSuccessor(LI->second);
}
Succ = B;
}
// Create an empty entry block that has no predecessors.
cfg->setEntry(createBlock());
// NULL out cfg so that repeated calls to the builder will fail and that
// the ownership of the constructed CFG is passed to the caller.
CFG* t = cfg;
cfg = NULL;
return t;
}
/// createBlock - Used to lazily create blocks that are connected
/// to the current (global) succcessor.
CFGBlock* CFGBuilder::createBlock(bool add_successor) {
CFGBlock* B = cfg->createBlock();
if (add_successor && Succ) B->addSuccessor(Succ);
return B;
}
/// FinishBlock - When the last statement has been added to the block,
/// we must reverse the statements because they have been inserted
/// in reverse order.
void CFGBuilder::FinishBlock(CFGBlock* B) {
assert (B);
B->reverseStmts();
}
/// addStmt - Used to add statements/expressions to the current CFGBlock
/// "Block". This method calls WalkAST on the passed statement to see if it
/// contains any short-circuit expressions. If so, it recursively creates
/// the necessary blocks for such expressions. It returns the "topmost" block
/// of the created blocks, or the original value of "Block" when this method
/// was called if no additional blocks are created.
CFGBlock* CFGBuilder::addStmt(Stmt* S) {
if (!Block) Block = createBlock();
return WalkAST(S,true);
}
/// WalkAST - Used by addStmt to walk the subtree of a statement and
/// add extra blocks for ternary operators, &&, and ||. We also
/// process "," and DeclStmts (which may contain nested control-flow).
CFGBlock* CFGBuilder::WalkAST(Stmt* S, bool AlwaysAddStmt = false) {
switch (S->getStmtClass()) {
case Stmt::ConditionalOperatorClass: {
ConditionalOperator* C = cast<ConditionalOperator>(S);
CFGBlock* ConfluenceBlock = (Block) ? Block : createBlock();
ConfluenceBlock->appendStmt(C);
FinishBlock(ConfluenceBlock);
Succ = ConfluenceBlock;
Block = NULL;
CFGBlock* LHSBlock = Visit(C->getLHS());
FinishBlock(LHSBlock);
Succ = ConfluenceBlock;
Block = NULL;
CFGBlock* RHSBlock = Visit(C->getRHS());
FinishBlock(RHSBlock);
Block = createBlock(false);
Block->addSuccessor(LHSBlock);
Block->addSuccessor(RHSBlock);
Block->setTerminator(C);
return addStmt(C->getCond());
}
case Stmt::ChooseExprClass: {
ChooseExpr* C = cast<ChooseExpr>(S);
CFGBlock* ConfluenceBlock = (Block) ? Block : createBlock();
ConfluenceBlock->appendStmt(C);
FinishBlock(ConfluenceBlock);
Succ = ConfluenceBlock;
Block = NULL;
CFGBlock* LHSBlock = Visit(C->getLHS());
FinishBlock(LHSBlock);
Succ = ConfluenceBlock;
Block = NULL;
CFGBlock* RHSBlock = Visit(C->getRHS());
FinishBlock(RHSBlock);
Block = createBlock(false);
Block->addSuccessor(LHSBlock);
Block->addSuccessor(RHSBlock);
Block->setTerminator(C);
return addStmt(C->getCond());
}
case Stmt::DeclStmtClass:
if (VarDecl* V = dyn_cast<VarDecl>(cast<DeclStmt>(S)->getDecl())) {
Block->appendStmt(S);
return WalkAST_VisitVarDecl(V);
}
else return Block;
case Stmt::AddrLabelExprClass: {
AddrLabelExpr* A = cast<AddrLabelExpr>(S);
AddressTakenLabels.insert(A->getLabel());
if (AlwaysAddStmt) Block->appendStmt(S);
return Block;
}
case Stmt::CallExprClass:
return WalkAST_VisitCallExpr(cast<CallExpr>(S));
case Stmt::StmtExprClass:
return WalkAST_VisitStmtExpr(cast<StmtExpr>(S));
case Stmt::BinaryOperatorClass: {
BinaryOperator* B = cast<BinaryOperator>(S);
if (B->isLogicalOp()) { // && or ||
CFGBlock* ConfluenceBlock = (Block) ? Block : createBlock();
ConfluenceBlock->appendStmt(B);
FinishBlock(ConfluenceBlock);
// create the block evaluating the LHS
CFGBlock* LHSBlock = createBlock(false);
LHSBlock->addSuccessor(ConfluenceBlock);
LHSBlock->setTerminator(B);
// create the block evaluating the RHS
Succ = ConfluenceBlock;
Block = NULL;
CFGBlock* RHSBlock = Visit(B->getRHS());
LHSBlock->addSuccessor(RHSBlock);
// Generate the blocks for evaluating the LHS.
Block = LHSBlock;
return addStmt(B->getLHS());
}
else if (B->getOpcode() == BinaryOperator::Comma) { // ,
Block->appendStmt(B);
addStmt(B->getRHS());
return addStmt(B->getLHS());
}
// Fall through to the default case.
}
default:
if (AlwaysAddStmt) Block->appendStmt(S);
return WalkAST_VisitChildren(S);
};
}
/// WalkAST_VisitVarDecl - Utility method to handle VarDecls contained in
/// DeclStmts. Because the initialization code for declarations can
/// contain arbitrary expressions, we must linearize declarations
/// to handle arbitrary control-flow induced by those expressions.
CFGBlock* CFGBuilder::WalkAST_VisitVarDecl(VarDecl* V) {
// We actually must parse the LAST declaration in a chain of
// declarations first, because we are building the CFG in reverse
// order.
if (Decl* D = V->getNextDeclarator())
if (VarDecl* Next = cast<VarDecl>(D))
Block = WalkAST_VisitVarDecl(Next);
if (Expr* E = V->getInit())
return addStmt(E);
assert (Block);
return Block;
}
/// WalkAST_VisitChildren - Utility method to call WalkAST on the
/// children of a Stmt.
CFGBlock* CFGBuilder::WalkAST_VisitChildren(Stmt* S) {
CFGBlock* B = Block;
for (Stmt::child_iterator I = S->child_begin(), E = S->child_end() ;
I != E; ++I)
if (*I) B = WalkAST(*I);
return B;
}
/// WalkAST_VisitStmtExpr - Utility method to handle (nested) statement
/// expressions (a GCC extension).
CFGBlock* CFGBuilder::WalkAST_VisitStmtExpr(StmtExpr* S) {
Block->appendStmt(S);
return VisitCompoundStmt(S->getSubStmt());
}
/// WalkAST_VisitCallExpr - Utility method to handle function calls that
/// are nested in expressions. The idea is that each function call should
/// appear as a distinct statement in the CFGBlock.
CFGBlock* CFGBuilder::WalkAST_VisitCallExpr(CallExpr* C) {
Block->appendStmt(C);
return WalkAST_VisitChildren(C);
}
/// VisitStmt - Handle statements with no branching control flow.
CFGBlock* CFGBuilder::VisitStmt(Stmt* Statement) {
// We cannot assume that we are in the middle of a basic block, since
// the CFG might only be constructed for this single statement. If
// we have no current basic block, just create one lazily.
if (!Block) Block = createBlock();
// Simply add the statement to the current block. We actually
// insert statements in reverse order; this order is reversed later
// when processing the containing element in the AST.
addStmt(Statement);
return Block;
}
CFGBlock* CFGBuilder::VisitNullStmt(NullStmt* Statement) {
return Block;
}
CFGBlock* CFGBuilder::VisitCompoundStmt(CompoundStmt* C) {
// The value returned from this function is the last created CFGBlock
// that represents the "entry" point for the translated AST node.
CFGBlock* LastBlock = 0;
for (CompoundStmt::reverse_body_iterator I = C->body_rbegin(),
E = C->body_rend(); I != E; ++I )
// Add the statement to the current block.
if (!(LastBlock=Visit(*I)))
return NULL;
return LastBlock;
}
CFGBlock* CFGBuilder::VisitIfStmt(IfStmt* I) {
// We may see an if statement in the middle of a basic block, or
// it may be the first statement we are processing. In either case,
// we create a new basic block. First, we create the blocks for
// the then...else statements, and then we create the block containing
// the if statement. If we were in the middle of a block, we
// stop processing that block and reverse its statements. That block
// is then the implicit successor for the "then" and "else" clauses.
// The block we were proccessing is now finished. Make it the
// successor block.
if (Block) {
Succ = Block;
FinishBlock(Block);
}
// Process the false branch. NULL out Block so that the recursive
// call to Visit will create a new basic block.
// Null out Block so that all successor
CFGBlock* ElseBlock = Succ;
if (Stmt* Else = I->getElse()) {
SaveAndRestore<CFGBlock*> sv(Succ);
// NULL out Block so that the recursive call to Visit will
// create a new basic block.
Block = NULL;
ElseBlock = Visit(Else);
if (!ElseBlock) // Can occur when the Else body has all NullStmts.
ElseBlock = sv.get();
else if (Block)
FinishBlock(ElseBlock);
}
// Process the true branch. NULL out Block so that the recursive
// call to Visit will create a new basic block.
// Null out Block so that all successor
CFGBlock* ThenBlock;
{
Stmt* Then = I->getThen();
assert (Then);
SaveAndRestore<CFGBlock*> sv(Succ);
Block = NULL;
ThenBlock = Visit(Then);
if (!ThenBlock) // Can occur when the Then body has all NullStmts.
ThenBlock = sv.get();
else if (Block)
FinishBlock(ThenBlock);
}
// Now create a new block containing the if statement.
Block = createBlock(false);
// Set the terminator of the new block to the If statement.
Block->setTerminator(I);
// Now add the successors.
Block->addSuccessor(ThenBlock);
Block->addSuccessor(ElseBlock);
// Add the condition as the last statement in the new block. This
// may create new blocks as the condition may contain control-flow. Any
// newly created blocks will be pointed to be "Block".
return addStmt(I->getCond());
}
CFGBlock* CFGBuilder::VisitReturnStmt(ReturnStmt* R) {
// If we were in the middle of a block we stop processing that block
// and reverse its statements.
//
// NOTE: If a "return" appears in the middle of a block, this means
// that the code afterwards is DEAD (unreachable). We still
// keep a basic block for that code; a simple "mark-and-sweep"
// from the entry block will be able to report such dead
// blocks.
if (Block) FinishBlock(Block);
// Create the new block.
Block = createBlock(false);
// The Exit block is the only successor.
Block->addSuccessor(&cfg->getExit());
// Add the return statement to the block. This may create new blocks
// if R contains control-flow (short-circuit operations).
return addStmt(R);
}
CFGBlock* CFGBuilder::VisitLabelStmt(LabelStmt* L) {
// Get the block of the labeled statement. Add it to our map.
CFGBlock* LabelBlock = Visit(L->getSubStmt());
if (!LabelBlock) // This can happen when the body is empty, i.e.
LabelBlock=createBlock(); // scopes that only contains NullStmts.
assert (LabelMap.find(L) == LabelMap.end() && "label already in map");
LabelMap[ L ] = LabelBlock;
// Labels partition blocks, so this is the end of the basic block
// we were processing (L is the block's label). Because this is
// label (and we have already processed the substatement) there is no
// extra control-flow to worry about.
LabelBlock->setLabel(L);
FinishBlock(LabelBlock);
// We set Block to NULL to allow lazy creation of a new block
// (if necessary);
Block = NULL;
// This block is now the implicit successor of other blocks.
Succ = LabelBlock;
return LabelBlock;
}
CFGBlock* CFGBuilder::VisitGotoStmt(GotoStmt* G) {
// Goto is a control-flow statement. Thus we stop processing the
// current block and create a new one.
if (Block) FinishBlock(Block);
Block = createBlock(false);
Block->setTerminator(G);
// If we already know the mapping to the label block add the
// successor now.
LabelMapTy::iterator I = LabelMap.find(G->getLabel());
if (I == LabelMap.end())
// We will need to backpatch this block later.
BackpatchBlocks.push_back(Block);
else
Block->addSuccessor(I->second);
return Block;
}
CFGBlock* CFGBuilder::VisitForStmt(ForStmt* F) {
// "for" is a control-flow statement. Thus we stop processing the
// current block.
CFGBlock* LoopSuccessor = NULL;
if (Block) {
FinishBlock(Block);
LoopSuccessor = Block;
}
else LoopSuccessor = Succ;
// Because of short-circuit evaluation, the condition of the loop
// can span multiple basic blocks. Thus we need the "Entry" and "Exit"
// blocks that evaluate the condition.
CFGBlock* ExitConditionBlock = createBlock(false);
CFGBlock* EntryConditionBlock = ExitConditionBlock;
// Set the terminator for the "exit" condition block.
ExitConditionBlock->setTerminator(F);
// Now add the actual condition to the condition block. Because the
// condition itself may contain control-flow, new blocks may be created.
if (Stmt* C = F->getCond()) {
Block = ExitConditionBlock;
EntryConditionBlock = addStmt(C);
if (Block) FinishBlock(EntryConditionBlock);
}
// The condition block is the implicit successor for the loop body as
// well as any code above the loop.
Succ = EntryConditionBlock;
// Now create the loop body.
{
assert (F->getBody());
// Save the current values for Block, Succ, and continue and break targets
SaveAndRestore<CFGBlock*> save_Block(Block), save_Succ(Succ),
save_continue(ContinueTargetBlock),
save_break(BreakTargetBlock);
// All continues within this loop should go to the condition block
ContinueTargetBlock = EntryConditionBlock;
// All breaks should go to the code following the loop.
BreakTargetBlock = LoopSuccessor;
// Create a new block to contain the (bottom) of the loop body.
Block = NULL;
// If we have increment code, insert it at the end of the body block.
if (Stmt* I = F->getInc()) Block = addStmt(I);
// Now populate the body block, and in the process create new blocks
// as we walk the body of the loop.
CFGBlock* BodyBlock = Visit(F->getBody());
if (!BodyBlock)
BodyBlock = ExitConditionBlock; // can happen for "for (...;...; ) ;"
else if (Block)
FinishBlock(BodyBlock);
// This new body block is a successor to our "exit" condition block.
ExitConditionBlock->addSuccessor(BodyBlock);
}
// Link up the condition block with the code that follows the loop.
// (the false branch).
ExitConditionBlock->addSuccessor(LoopSuccessor);
// If the loop contains initialization, create a new block for those
// statements. This block can also contain statements that precede
// the loop.
if (Stmt* I = F->getInit()) {
Block = createBlock();
return addStmt(I);
}
else {
// There is no loop initialization. We are thus basically a while
// loop. NULL out Block to force lazy block construction.
Block = NULL;
return EntryConditionBlock;
}
}
CFGBlock* CFGBuilder::VisitWhileStmt(WhileStmt* W) {
// "while" is a control-flow statement. Thus we stop processing the
// current block.
CFGBlock* LoopSuccessor = NULL;
if (Block) {
FinishBlock(Block);
LoopSuccessor = Block;
}
else LoopSuccessor = Succ;
// Because of short-circuit evaluation, the condition of the loop
// can span multiple basic blocks. Thus we need the "Entry" and "Exit"
// blocks that evaluate the condition.
CFGBlock* ExitConditionBlock = createBlock(false);
CFGBlock* EntryConditionBlock = ExitConditionBlock;
// Set the terminator for the "exit" condition block.
ExitConditionBlock->setTerminator(W);
// Now add the actual condition to the condition block. Because the
// condition itself may contain control-flow, new blocks may be created.
// Thus we update "Succ" after adding the condition.
if (Stmt* C = W->getCond()) {
Block = ExitConditionBlock;
EntryConditionBlock = addStmt(C);
if (Block) FinishBlock(EntryConditionBlock);
}
// The condition block is the implicit successor for the loop body as
// well as any code above the loop.
Succ = EntryConditionBlock;
// Process the loop body.
{
assert (W->getBody());
// Save the current values for Block, Succ, and continue and break targets
SaveAndRestore<CFGBlock*> save_Block(Block), save_Succ(Succ),
save_continue(ContinueTargetBlock),
save_break(BreakTargetBlock);
// All continues within this loop should go to the condition block
ContinueTargetBlock = EntryConditionBlock;
// All breaks should go to the code following the loop.
BreakTargetBlock = LoopSuccessor;
// NULL out Block to force lazy instantiation of blocks for the body.
Block = NULL;
// Create the body. The returned block is the entry to the loop body.
CFGBlock* BodyBlock = Visit(W->getBody());
if (!BodyBlock)
BodyBlock = ExitConditionBlock; // can happen for "while(...) ;"
else if (Block)
FinishBlock(BodyBlock);
// Add the loop body entry as a successor to the condition.
ExitConditionBlock->addSuccessor(BodyBlock);
}
// Link up the condition block with the code that follows the loop.
// (the false branch).
ExitConditionBlock->addSuccessor(LoopSuccessor);
// There can be no more statements in the condition block
// since we loop back to this block. NULL out Block to force
// lazy creation of another block.
Block = NULL;
// Return the condition block, which is the dominating block for the loop.
return EntryConditionBlock;
}
CFGBlock* CFGBuilder::VisitDoStmt(DoStmt* D) {
// "do...while" is a control-flow statement. Thus we stop processing the
// current block.
CFGBlock* LoopSuccessor = NULL;
if (Block) {
FinishBlock(Block);
LoopSuccessor = Block;
}
else LoopSuccessor = Succ;
// Because of short-circuit evaluation, the condition of the loop
// can span multiple basic blocks. Thus we need the "Entry" and "Exit"
// blocks that evaluate the condition.
CFGBlock* ExitConditionBlock = createBlock(false);
CFGBlock* EntryConditionBlock = ExitConditionBlock;
// Set the terminator for the "exit" condition block.
ExitConditionBlock->setTerminator(D);
// Now add the actual condition to the condition block. Because the
// condition itself may contain control-flow, new blocks may be created.
if (Stmt* C = D->getCond()) {
Block = ExitConditionBlock;
EntryConditionBlock = addStmt(C);
if (Block) FinishBlock(EntryConditionBlock);
}
// The condition block is the implicit successor for the loop body as
// well as any code above the loop.
Succ = EntryConditionBlock;
// Process the loop body.
CFGBlock* BodyBlock = NULL;
{
assert (D->getBody());
// Save the current values for Block, Succ, and continue and break targets
SaveAndRestore<CFGBlock*> save_Block(Block), save_Succ(Succ),
save_continue(ContinueTargetBlock),
save_break(BreakTargetBlock);
// All continues within this loop should go to the condition block
ContinueTargetBlock = EntryConditionBlock;
// All breaks should go to the code following the loop.
BreakTargetBlock = LoopSuccessor;
// NULL out Block to force lazy instantiation of blocks for the body.
Block = NULL;
// Create the body. The returned block is the entry to the loop body.
BodyBlock = Visit(D->getBody());
if (!BodyBlock)
BodyBlock = ExitConditionBlock; // can happen for "do ; while(...)"
else if (Block)
FinishBlock(BodyBlock);
// Add the loop body entry as a successor to the condition.
ExitConditionBlock->addSuccessor(BodyBlock);
}
// Link up the condition block with the code that follows the loop.
// (the false branch).
ExitConditionBlock->addSuccessor(LoopSuccessor);
// There can be no more statements in the body block(s)
// since we loop back to the body. NULL out Block to force
// lazy creation of another block.
Block = NULL;
// Return the loop body, which is the dominating block for the loop.
return BodyBlock;
}
CFGBlock* CFGBuilder::VisitContinueStmt(ContinueStmt* C) {
// "continue" is a control-flow statement. Thus we stop processing the
// current block.
if (Block) FinishBlock(Block);
// Now create a new block that ends with the continue statement.
Block = createBlock(false);
Block->setTerminator(C);
// If there is no target for the continue, then we are looking at an
// incomplete AST. Handle this by not registering a successor.
if (ContinueTargetBlock) Block->addSuccessor(ContinueTargetBlock);
return Block;
}
CFGBlock* CFGBuilder::VisitBreakStmt(BreakStmt* B) {
// "break" is a control-flow statement. Thus we stop processing the
// current block.
if (Block) FinishBlock(Block);
// Now create a new block that ends with the continue statement.
Block = createBlock(false);
Block->setTerminator(B);
// If there is no target for the break, then we are looking at an
// incomplete AST. Handle this by not registering a successor.
if (BreakTargetBlock) Block->addSuccessor(BreakTargetBlock);
return Block;
}
CFGBlock* CFGBuilder::VisitSwitchStmt(SwitchStmt* S) {
// "switch" is a control-flow statement. Thus we stop processing the
// current block.
CFGBlock* SwitchSuccessor = NULL;
if (Block) {
FinishBlock(Block);
SwitchSuccessor = Block;
}
else SwitchSuccessor = Succ;
// Save the current "switch" context.
SaveAndRestore<CFGBlock*> save_switch(SwitchTerminatedBlock),
save_break(BreakTargetBlock);
// Create a new block that will contain the switch statement.
SwitchTerminatedBlock = createBlock(false);
// Now process the switch body. The code after the switch is the implicit
// successor.
Succ = SwitchSuccessor;
BreakTargetBlock = SwitchSuccessor;
// When visiting the body, the case statements should automatically get
// linked up to the switch. We also don't keep a pointer to the body,
// since all control-flow from the switch goes to case/default statements.
assert (S->getBody() && "switch must contain a non-NULL body");
Block = NULL;
CFGBlock *BodyBlock = Visit(S->getBody());
if (Block) FinishBlock(BodyBlock);
// Add the terminator and condition in the switch block.
SwitchTerminatedBlock->setTerminator(S);
assert (S->getCond() && "switch condition must be non-NULL");
Block = SwitchTerminatedBlock;
return addStmt(S->getCond());
}
CFGBlock* CFGBuilder::VisitSwitchCase(SwitchCase* S) {
// A SwitchCase is either a "default" or "case" statement. We handle
// both in the same way. They are essentially labels, so they are the
// first statement in a block.
if (S->getSubStmt()) Visit(S->getSubStmt());
CFGBlock* CaseBlock = Block;
if (!CaseBlock) CaseBlock = createBlock();
// Cases/Default statements partition block, so this is the top of
// the basic block we were processing (the case/default is the label).
CaseBlock->setLabel(S);
FinishBlock(CaseBlock);
// Add this block to the list of successors for the block with the
// switch statement.
if (SwitchTerminatedBlock) SwitchTerminatedBlock->addSuccessor(CaseBlock);
// We set Block to NULL to allow lazy creation of a new block (if necessary)
Block = NULL;
// This block is now the implicit successor of other blocks.
Succ = CaseBlock;
return CaseBlock;
}
CFGBlock* CFGBuilder::VisitIndirectGotoStmt(IndirectGotoStmt* I) {
// Lazily create the indirect-goto dispatch block if there isn't one
// already.
CFGBlock* IBlock = cfg->getIndirectGotoBlock();
if (!IBlock) {
IBlock = createBlock(false);
cfg->setIndirectGotoBlock(IBlock);
}
// IndirectGoto is a control-flow statement. Thus we stop processing the
// current block and create a new one.
if (Block) FinishBlock(Block);
Block = createBlock(false);
Block->setTerminator(I);
Block->addSuccessor(IBlock);
return addStmt(I->getTarget());
}
} // end anonymous namespace
/// createBlock - Constructs and adds a new CFGBlock to the CFG. The
/// block has no successors or predecessors. If this is the first block
/// created in the CFG, it is automatically set to be the Entry and Exit
/// of the CFG.
CFGBlock* CFG::createBlock() {
bool first_block = begin() == end();
// Create the block.
Blocks.push_front(CFGBlock(NumBlockIDs++));
// If this is the first block, set it as the Entry and Exit.
if (first_block) Entry = Exit = &front();
// Return the block.
return &front();
}
/// buildCFG - Constructs a CFG from an AST. Ownership of the returned
/// CFG is returned to the caller.
CFG* CFG::buildCFG(Stmt* Statement) {
CFGBuilder Builder;
return Builder.buildCFG(Statement);
}
/// reverseStmts - Reverses the orders of statements within a CFGBlock.
void CFGBlock::reverseStmts() { std::reverse(Stmts.begin(),Stmts.end()); }
//===----------------------------------------------------------------------===//
// CFG: Queries for BlkExprs.
//===----------------------------------------------------------------------===//
namespace {
typedef llvm::DenseMap<const Expr*,unsigned> BlkExprMapTy;
}
static BlkExprMapTy* PopulateBlkExprMap(CFG& cfg) {
BlkExprMapTy* M = new BlkExprMapTy();
for (CFG::iterator I=cfg.begin(), E=cfg.end(); I != E; ++I)
for (CFGBlock::iterator BI=I->begin(), EI=I->end(); BI != EI; ++BI)
if (const Expr* E = dyn_cast<Expr>(*BI))
(*M)[E] = M->size();
return M;
}
bool CFG::isBlkExpr(const Stmt* S) {
assert (S != NULL);
if (const Expr* E = dyn_cast<Expr>(S)) return getBlkExprNum(E);
else return true; // Statements are by default "block-level expressions."
}
CFG::BlkExprNumTy CFG::getBlkExprNum(const Expr* E) {
assert(E != NULL);
if (!BlkExprMap) { BlkExprMap = (void*) PopulateBlkExprMap(*this); }
BlkExprMapTy* M = reinterpret_cast<BlkExprMapTy*>(BlkExprMap);
BlkExprMapTy::iterator I = M->find(E);
if (I == M->end()) return CFG::BlkExprNumTy();
else return CFG::BlkExprNumTy(I->second);
}
unsigned CFG::getNumBlkExprs() {
if (const BlkExprMapTy* M = reinterpret_cast<const BlkExprMapTy*>(BlkExprMap))
return M->size();
else {
// We assume callers interested in the number of BlkExprs will want
// the map constructed if it doesn't already exist.
BlkExprMap = (void*) PopulateBlkExprMap(*this);
return reinterpret_cast<BlkExprMapTy*>(BlkExprMap)->size();
}
}
CFG::~CFG() {
delete reinterpret_cast<const BlkExprMapTy*>(BlkExprMap);
}
//===----------------------------------------------------------------------===//
// CFG pretty printing
//===----------------------------------------------------------------------===//
namespace {
class StmtPrinterHelper : public PrinterHelper {
typedef llvm::DenseMap<Stmt*,std::pair<unsigned,unsigned> > StmtMapTy;
StmtMapTy StmtMap;
signed CurrentBlock;
unsigned CurrentStmt;
public:
StmtPrinterHelper(const CFG* cfg) : CurrentBlock(0), CurrentStmt(0) {
for (CFG::const_iterator I = cfg->begin(), E = cfg->end(); I != E; ++I ) {
unsigned j = 1;
for (CFGBlock::const_iterator BI = I->begin(), BEnd = I->end() ;
BI != BEnd; ++BI, ++j )
StmtMap[*BI] = std::make_pair(I->getBlockID(),j);
}
}
virtual ~StmtPrinterHelper() {}
void setBlockID(signed i) { CurrentBlock = i; }
void setStmtID(unsigned i) { CurrentStmt = i; }
virtual bool handledStmt(Stmt* S, std::ostream& OS) {
StmtMapTy::iterator I = StmtMap.find(S);
if (I == StmtMap.end())
return false;
if (CurrentBlock >= 0 && I->second.first == (unsigned) CurrentBlock
&& I->second.second == CurrentStmt)
return false;
OS << "[B" << I->second.first << "." << I->second.second << "]";
return true;
}
};
class CFGBlockTerminatorPrint : public StmtVisitor<CFGBlockTerminatorPrint,
void >
{
std::ostream& OS;
StmtPrinterHelper* Helper;
public:
CFGBlockTerminatorPrint(std::ostream& os, StmtPrinterHelper* helper)
: OS(os), Helper(helper) {}
void VisitIfStmt(IfStmt* I) {
OS << "if ";
I->getCond()->printPretty(OS,Helper);
OS << "\n";
}
// Default case.
void VisitStmt(Stmt* S) { S->printPretty(OS); }
void VisitForStmt(ForStmt* F) {
OS << "for (" ;
if (F->getInit()) OS << "...";
OS << "; ";
if (Stmt* C = F->getCond()) C->printPretty(OS,Helper);
OS << "; ";
if (F->getInc()) OS << "...";
OS << ")\n";
}
void VisitWhileStmt(WhileStmt* W) {
OS << "while " ;
if (Stmt* C = W->getCond()) C->printPretty(OS,Helper);
OS << "\n";
}
void VisitDoStmt(DoStmt* D) {
OS << "do ... while ";
if (Stmt* C = D->getCond()) C->printPretty(OS,Helper);
OS << '\n';
}
void VisitSwitchStmt(SwitchStmt* S) {
OS << "switch ";
S->getCond()->printPretty(OS,Helper);
OS << '\n';
}
void VisitConditionalOperator(ConditionalOperator* C) {
C->getCond()->printPretty(OS,Helper);
OS << " ? ... : ...\n";
}
void VisitChooseExpr(ChooseExpr* C) {
OS << "__builtin_choose_expr( ";
C->getCond()->printPretty(OS,Helper);
OS << " )\n";
}
void VisitIndirectGotoStmt(IndirectGotoStmt* I) {
OS << "goto *";
I->getTarget()->printPretty(OS,Helper);
OS << '\n';
}
void VisitBinaryOperator(BinaryOperator* B) {
if (!B->isLogicalOp()) {
VisitExpr(B);
return;
}
B->getLHS()->printPretty(OS,Helper);
switch (B->getOpcode()) {
case BinaryOperator::LOr:
OS << " || ...\n";
return;
case BinaryOperator::LAnd:
OS << " && ...\n";
return;
default:
assert(false && "Invalid logical operator.");
}
}
void VisitExpr(Expr* E) {
E->printPretty(OS,Helper);
OS << '\n';
}
};
void print_stmt(std::ostream&OS, StmtPrinterHelper* Helper, Stmt* S) {
if (Helper) {
// special printing for statement-expressions.
if (StmtExpr* SE = dyn_cast<StmtExpr>(S)) {
CompoundStmt* Sub = SE->getSubStmt();
if (Sub->child_begin() != Sub->child_end()) {
OS << "({ ... ; ";
Helper->handledStmt(*SE->getSubStmt()->child_rbegin(),OS);
OS << " })\n";
return;
}
}
// special printing for comma expressions.
if (BinaryOperator* B = dyn_cast<BinaryOperator>(S)) {
if (B->getOpcode() == BinaryOperator::Comma) {
OS << "... , ";
Helper->handledStmt(B->getRHS(),OS);
OS << '\n';
return;
}
}
}
S->printPretty(OS, Helper);
// Expressions need a newline.
if (isa<Expr>(S)) OS << '\n';
}
void print_block(std::ostream& OS, const CFG* cfg, const CFGBlock& B,
StmtPrinterHelper* Helper, bool print_edges) {
if (Helper) Helper->setBlockID(B.getBlockID());
// Print the header.
OS << "\n [ B" << B.getBlockID();
if (&B == &cfg->getEntry())
OS << " (ENTRY) ]\n";
else if (&B == &cfg->getExit())
OS << " (EXIT) ]\n";
else if (&B == cfg->getIndirectGotoBlock())
OS << " (INDIRECT GOTO DISPATCH) ]\n";
else
OS << " ]\n";
// Print the label of this block.
if (Stmt* S = const_cast<Stmt*>(B.getLabel())) {
if (print_edges)
OS << " ";
if (LabelStmt* L = dyn_cast<LabelStmt>(S))
OS << L->getName();
else if (CaseStmt* C = dyn_cast<CaseStmt>(S)) {
OS << "case ";
C->getLHS()->printPretty(OS);
if (C->getRHS()) {
OS << " ... ";
C->getRHS()->printPretty(OS);
}
}
else if (isa<DefaultStmt>(S))
OS << "default";
else
assert(false && "Invalid label statement in CFGBlock.");
OS << ":\n";
}
// Iterate through the statements in the block and print them.
unsigned j = 1;
for (CFGBlock::const_iterator I = B.begin(), E = B.end() ;
I != E ; ++I, ++j ) {
// Print the statement # in the basic block and the statement itself.
if (print_edges)
OS << " ";
OS << std::setw(3) << j << ": ";
if (Helper)
Helper->setStmtID(j);
print_stmt(OS,Helper,*I);
}
// Print the terminator of this block.
if (B.getTerminator()) {
if (print_edges)
OS << " ";
OS << " T: ";
if (Helper) Helper->setBlockID(-1);
CFGBlockTerminatorPrint TPrinter(OS,Helper);
TPrinter.Visit(const_cast<Stmt*>(B.getTerminator()));
}
if (print_edges) {
// Print the predecessors of this block.
OS << " Predecessors (" << B.pred_size() << "):";
unsigned i = 0;
for (CFGBlock::const_pred_iterator I = B.pred_begin(), E = B.pred_end();
I != E; ++I, ++i) {
if (i == 8 || (i-8) == 0)
OS << "\n ";
OS << " B" << (*I)->getBlockID();
}
OS << '\n';
// Print the successors of this block.
OS << " Successors (" << B.succ_size() << "):";
i = 0;
for (CFGBlock::const_succ_iterator I = B.succ_begin(), E = B.succ_end();
I != E; ++I, ++i) {
if (i == 8 || (i-8) % 10 == 0)
OS << "\n ";
OS << " B" << (*I)->getBlockID();
}
OS << '\n';
}
}
} // end anonymous namespace
/// dump - A simple pretty printer of a CFG that outputs to stderr.
void CFG::dump() const { print(std::cerr); }
/// print - A simple pretty printer of a CFG that outputs to an ostream.
void CFG::print(std::ostream& OS) const {
StmtPrinterHelper Helper(this);
// Print the entry block.
print_block(OS, this, getEntry(), &Helper, true);
// Iterate through the CFGBlocks and print them one by one.
for (const_iterator I = Blocks.begin(), E = Blocks.end() ; I != E ; ++I) {
// Skip the entry block, because we already printed it.
if (&(*I) == &getEntry() || &(*I) == &getExit())
continue;
print_block(OS, this, *I, &Helper, true);
}
// Print the exit block.
print_block(OS, this, getExit(), &Helper, true);
}
/// dump - A simply pretty printer of a CFGBlock that outputs to stderr.
void CFGBlock::dump(const CFG* cfg) const { print(std::cerr, cfg); }
/// print - A simple pretty printer of a CFGBlock that outputs to an ostream.
/// Generally this will only be called from CFG::print.
void CFGBlock::print(std::ostream& OS, const CFG* cfg) const {
StmtPrinterHelper Helper(cfg);
print_block(OS, cfg, *this, &Helper, true);
}
//===----------------------------------------------------------------------===//
// CFG Graphviz Visualization
//===----------------------------------------------------------------------===//
#ifndef NDEBUG
static StmtPrinterHelper* GraphHelper;
#endif
void CFG::viewCFG() const {
#ifndef NDEBUG
StmtPrinterHelper H(this);
GraphHelper = &H;
llvm::ViewGraph(this,"CFG");
GraphHelper = NULL;
#else
std::cerr << "CFG::viewCFG is only available in debug builds on "
<< "systems with Graphviz or gv!\n";
#endif
}
namespace llvm {
template<>
struct DOTGraphTraits<const CFG*> : public DefaultDOTGraphTraits {
static std::string getNodeLabel(const CFGBlock* Node, const CFG* Graph) {
#ifndef NDEBUG
std::ostringstream Out;
print_block(Out,Graph, *Node, GraphHelper, false);
std::string OutStr = Out.str();
if (OutStr[0] == '\n') OutStr.erase(OutStr.begin());
// Process string output to make it nicer...
for (unsigned i = 0; i != OutStr.length(); ++i)
if (OutStr[i] == '\n') { // Left justify
OutStr[i] = '\\';
OutStr.insert(OutStr.begin()+i+1, 'l');
}
return OutStr;
#else
return "";
#endif
}
};
} // end namespace llvm